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1.
The development of many complex stratified lichen thalli is made through stages of complex phenotypic interactions between
a filamentous fungus (the mycobiont), and a trebouxioid alga (the photobiont). Typically, the second stage of this symbiotic
development is marked by the envelopment of the photobiont by the mycobiont through increased lateral hyphal branching and
the formation of appressoria. Previously, the mycobiont’s envelopment of photobiont cells was considered thigmotropic (a growth
response due to shape) as a mycobiont can envelop algal sized objects in its environment. However, after growing the mycobiontCladonia grayi with various phototrophs and glass beads, we conclude that the mycobiont does not show this characteristic second stage morphological
response when grown in non-compatible pairings. Instead,C. grayi displays a distinctive morphological growth response only in compatible symbiotic pairings, such as with its natural photobiontAsterochlor’is sp. 相似文献
2.
Fungal specificity and selectivity for algae play a major role in determining lichen partnerships across diverse ecogeographic regions in the lichen‐forming family Parmeliaceae (Ascomycota)
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Steven D. Leavitt Ekaphan Kraichak Matthew P. Nelsen Susanne Altermann Pradeep K. Divakar David Alors Theodore L. Esslinger Ana Crespo Thorsten Lumbsch 《Molecular ecology》2015,24(14):3779-3797
Microbial symbionts are instrumental to the ecological and long‐term evolutionary success of their hosts, and the central role of symbiotic interactions is increasingly recognized across the vast majority of life. Lichens provide an iconic group for investigating patterns in species interactions; however, relationships among lichen symbionts are often masked by uncertain species boundaries or an inability to reliably identify symbionts. The species‐rich lichen‐forming fungal family Parmeliaceae provides a diverse group for assessing patterns of interactions of algal symbionts, and our study addresses patterns of lichen symbiont interactions at the largest geographic and taxonomic scales attempted to date. We analysed a total of 2356 algal internal transcribed spacer (ITS) region sequences collected from lichens representing ten mycobiont genera in Parmeliaceae, two genera in Lecanoraceae and 26 cultured Trebouxia strains. Algal ITS sequences were grouped into operational taxonomic units (OTUs); we attempted to validate the evolutionary independence of a subset of the inferred OTUs using chloroplast and mitochondrial loci. We explored the patterns of symbiont interactions in these lichens based on ecogeographic distributions and mycobiont taxonomy. We found high levels of undescribed diversity in Trebouxia, broad distributions across distinct ecoregions for many photobiont OTUs and varying levels of mycobiont selectivity and specificity towards the photobiont. Based on these results, we conclude that fungal specificity and selectivity for algal partners play a major role in determining lichen partnerships, potentially superseding ecology, at least at the ecogeographic scale investigated here. To facilitate effective communication and consistency across future studies, we propose a provisional naming system for Trebouxia photobionts and provide representative sequences for each OTU circumscribed in this study. 相似文献
3.
Yan-Yan Wang Tao Zhang Qi-Ming Zhou Jiang-Chun Wei 《World journal of microbiology & biotechnology》2011,27(12):2873-2884
The first full-length cDNA library for lichenized fungi was constructed from cultured mycobiont of the arid desert lichen
Endocarpon pusillum. Based on small-scale sequencing results, 111 genes of the lichenized fungi were identified for the first time, among which
11 genes shared no homology with any known fungal genes. Real-time PCR showed that the size of the mycobiont genome is 39.13 Mb
and the copy number of ribosomal RNA gene repeat units is 43. The results of this study will be valuable for the ongoing lichen
genome-sequencing project and the large-scale identification of functional genes from lichenized fungi. 相似文献
4.
二氧化硫对地衣中共生藻菌营养关系影响研究 总被引:6,自引:1,他引:5
为探讨地衣对大气污染特别敏感的原因 ,分离淡腹黄梅衣 (Xanthoparmelliamexicana)的共生藻和共生真菌 ,并重新合成地衣 .研究了地衣及纯化培养的藻和菌在SO2 污染短期胁迫下的生理反应 .结果表明 ,叶绿素a比叶绿素b易受伤害 ;叶绿素对 0 .5mg·L-1的熏气最敏感 ,水溶液暴露时叶绿素PQa值的下降与SO2 的吸收量有相关性 .地衣中酸性磷酸酶活性主要由共生藻所决定 .丙二醇含量在共生藻和菌以及地衣样品中无显著差异 ;还原型谷胱甘肽GSH含量在共生菌中明显高于共生藻 ,并与SO2 胁迫强度密切相关 .可以作为地衣过氧化状态和受损的生物标志物 .共生真菌承担了地衣主要的抗氧化任务 ,由于物质与能量的消耗 ,共生藻比共生菌更容易受到伤害 . 相似文献
5.
Quantifying the climatic niche of symbiont partners in a lichen symbiosis indicates mutualist‐mediated niche expansions
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Gregor Rolshausen Francesco Dal Grande Anna D. Sadowska‐Deś Jürgen Otte Imke Schmitt 《Ecography》2018,41(8):1380-1392
The large distributional areas and ecological niches of many lichenized fungi may in part be due to the plasticity in interactions between the fungus (mycobiont) and its algal or cyanobacterial partners (photobionts). On the one hand, broad‐scale phylogenetic analyses show that partner compatibility in lichens is rather constrained and shaped by reciprocal selection pressures and codiversification independent of ecological drivers. On the other hand, sub‐species‐level associations among lichen symbionts appear to be environmentally structured rather than phylogenetically constrained. In particular, switching between photobiont ecotypes with distinct environmental preferences has been hypothesized as an adaptive strategy for lichen‐forming fungi to broaden their ecological niche. The extent and direction of photobiont‐mediated range expansions in lichens, however, have not been examined comprehensively at a broad geographic scale. Here we investigate the population genetic structure of Lasallia pustulata symbionts at sub‐species‐level resolution across the mycobiont's Europe‐wide range, using fungal MCM7 and algal ITS rDNA sequence markers. We show that variance in occurrence probabilities in the geographic distribution of genetic diversity in mycobiont‐photobiont interactions is closely related to changes in climatic niches. Quantification of niche extent and overlap based on species distribution modeling and construction of Hutchinsonian climatic hypervolumes revealed that combinations of fungal–algal interactions change at the sub‐species level along latitudinal temperature gradients and in Mediterranean climate zones. Our study provides evidence for symbiont‐mediated niche expansion in lichens. We discuss our results in the light of symbiont polymorphism and partner switching as potential mechanisms of environmental adaptation and niche evolution in mutualisms. 相似文献
6.
David J. Hill 《The Botanical review》2009,75(3):326-338
It is proposed that lichen photobionts, compared to mycobionts, have very limited capacity to evolve adaptations to lichenization,
so that the symbionts in lichens do not co-evolve. This is because lichens have (a) no sequential selection of photobiont
cells from one lichen into another needed for Darwinian natural selection and (b) no photobiont sexual reproduction in the
thallus. Molecular studies of lichen photobionts indicate no predictable patterns of photobiont lineages that occur in lichens
so supporting this proposal. Any adaptation by photobionts accumulating beneficial mutations for lichenization is probably
insignificant compared to the rate of mycobiont adaptation. This proposal poses questions for research relating the photobiont
sexual cycle (genetic and cellular), the fate of photobiont lineages after lichenization, whether lineages of photobionts
in thalli change with time, thallus formation by from spores as well as carbohydrate movement from photobionts to mycobionts
and regulation of co-development of the symbionts in the thallus. 相似文献
7.
Domestication of algae by lichen‐forming fungi describes the symbiotic relationship between the photosynthetic (green alga or cyanobacterium; photobiont) and fungal (mycobiont) partnership in lichen associations ( Goward 1992 ). The algal domestication implies that the mycobiont cultivates the alga as a monoculture within its thallus, analogous to a farmer cultivating a food crop. However, the initial photobiont ‘selection’ by the mycobiont may be predetermined by the habitat rather than by the farmer. When the mycobiont selects a photobiont from the available photobionts within a habitat, the mycobiont may influence photobiont growth and reproduction ( Ahmadjian & Jacobs 1981 ) only after the interaction has been initiated. The theory of ecological guilds ( Rikkinen et al. 2002 ) proposes that habitat limits the variety of photobionts available to the fungal partner. While some studies provide evidence to support the theory of ecological guilds in cyanobacterial lichens ( Rikkinen et al. 2002 ), other studies propose models to explain variation in symbiont combinations in green algal lichens ( Ohmura et al. 2006 ; Piercey‐Normore 2006 ; Yahr et al. 2006 ) hypothesizing the existence of such guilds. In this issue of Molecular Ecology, Peksa & ?kaloud (2011) test the theory of ecological guilds and suggest a relationship between algal habitat requirements and lichen adaptation in green algal lichens of the genus Lepraria. The environmental parameters examined in this study, exposure to rainfall, altitude and substratum type, are integral to lichen biology. Lichens have a poikilohydric nature, relying on the availability of atmospheric moisture for metabolic processes. Having no known active mechanism to preserve metabolic thallus moisture in times of drought, one would expect a strong influence of the environment on symbiont adaptation to specific habitats. Adaptation to changes in substrata and its properties would be expected with the intimate contact between crustose lichens in the genus Lepraria. Altitude has been suggested to influence species distributions in a wide range of taxonomic groups. This is one of the first studies to illustrate an ecological guild, mainly for exposure to rainfall (ombrophiles and ombrophobes), with green algal lichens. 相似文献
8.
Cristina Branquinho Paula MatosAna Rute Vieira Maria Margarida Prestello Ramos 《Environmental and Experimental Botany》2011,72(1):84-92
The relative impact of lichen photobiont and mycobiont was evaluated by submitting nine lichen species with: (i) different photobiont types; (ii) different lichen growth forms; and (iii) different nutrients, pH, humidity preferences; to a range of Cu concentrations (μM) supplied in repeated cycles to simulate the natural process of uptake under field conditions. The physiological performance of the photosystem II photochemical reactions was measured using Fv/Fm and the metabolic activity of the mycobiont was evaluated using ergosterol and intracellular K-loss as indicators. Lichens with higher cation exchange capacity showed higher intracellular Cu uptake and their ecology seemed to be associated with low-nutrient environments. Thus the wall and external matrix, mainly characteristic of the mycobiont partner, cannot be ignored as the first site of interaction of metals with lichens. No common intracellular Cu concentration threshold was found for the physiological impacts observed in the different species. Most physiological effects of Cu uptake in sensitive lichens occurred for intracellular Cu below 200 μg/g dw whereas more tolerant species were able to cope with intracellular Cu at least 3 times higher. Cyanobacterial lichens showed to be more sensitive to Cu uptake than green-algal lichens. Within the Trebouxia lichens, different species showed different sensitivities to Cu uptake, suggesting that the mycobiont may change the microenvironment close to the photobiont partner providing different degrees of protection. Despite the fact that the photobiont is the productive partner, the metabolic activity of the mycobiont of lichen species adapted to environments rich in nutrients, showed to be more sensitive to Cu uptake than the photochemical performance of the photobiont. 相似文献
9.
《Fungal Ecology》2022
We tested the congruence in dispersal patterns of the two main symbionts of the lichen Cladonia stellaris using genotyping-by-sequencing data. Based on 122 samples from eastern Canada, we recovered more than 21000 loci from the photobiont of C. stellaris. We described the population structure and estimate genetic diversity of the photobiont and identified the factors that contribute to explain genetic variation in both lichen partners. We also determined the identity of the dominant photobiont associated to C. stellaris using two molecular markers. Our results showed that C. stellaris is associated with Asterochloris glomerata, A. irregularis, and A. pseudoirregularis. Congruence in the genetic structure of photobiont and mycobiont were confirmed, suggesting co-dispersal of thallus fragments of C. stellaris. Genetic diversity of each symbiont was the factor that explained most of the genetic variation of the other symbiont, whereas geographical location and bioclimatic region seemed to have small or null explanatory power. 相似文献
10.
Reis RA Iacomini M Gorin PA de Souza LM Grube M Cordeiro LM Sassaki GL 《FEMS microbiology letters》2005,249(1):1-6
Fatty acid components, in both the free and combined form of the intact tropical lichen Teloschistes flavicans, and its isolated photobiont and mycobiont, were analyzed by GC-MS of derived methyl esters. Its rDNA analysis confirmed that the isolated cultured symbionts belong to the genera Trebouxia and Teloschistes, respectively. The fatty acid composition of the lichen did not correspond to those found in the isolated symbionts, suggesting that the fatty acid metabolism is markedly influenced by the symbiosis. Differences in the fatty acid composition in the lichen were observed during the summer (27 degrees C), when the main fatty acids were saturated and in the winter (22 degrees C) when an increase of unsaturated fatty acids occurred. Similar differences of composition were also observed for the cultured mycobiont at different temperatures. The increase in the unsaturation level at low temperatures would maintain the membrane fluidity. Our results are the first on the fatty acids of a tropical lichen and suggest that it is sensitive to small temperature variations, which influences its saturated and unsaturated fatty acid composition. 相似文献
11.
Summary A protein fraction, previously isolated from the lichenXanthoria parietina and known to bind to the appropriate culturedTrebouxia phycobiont, was visualized in the intact lichen thallus and cultured mycobiont by an indirect immunoperoxidase assay. The protein was localized in both the upper and lower cortices of the lichen thallus; it was also present in the cell walls of the mycobiont culturedin vitro. The possible role of this protein in the recognition, or initial interaction, between separated lichen symbionts is discussed. 相似文献
12.
Fernández-Mendoza F Domaschke S García MA Jordan P Martín MP Printzen C 《Molecular ecology》2011,20(6):1208-1232
Lichens are symbioses between fungi (mycobionts) and photoautotrophic green algae or cyanobacteria (photobionts). Many lichens occupy large distributional ranges covering several climatic zones. So far, little is known about the large‐scale phylogeography of lichen photobionts and their role in shaping the distributional ranges of lichens. We studied south polar, temperate and north polar populations of the widely distributed fruticose lichen Cetraria aculeata. Based on the DNA sequences from three loci for each symbiont, we compared the genetic structure of mycobionts and photobionts. Phylogenetic reconstructions and Bayesian clustering methods divided the mycobiont and photobiont data sets into three groups. An amova shows that the genetic variance of the photobiont is best explained by differentiation between temperate and polar regions and that of the mycobiont by an interaction of climatic and geographical factors. By partialling out the relative contribution of climate, geography and codispersal, we found that the most relevant factors shaping the genetic structure of the photobiont are climate and a history of codispersal. Mycobionts in the temperate region are consistently associated with a specific photobiont lineage. We therefore conclude that a photobiont switch in the past enabled C. aculeata to colonize temperate as well as polar habitats. Rare photobiont switches may increase the geographical range and ecological niche of lichen mycobionts by associating them with locally adapted photobionts in climatically different regions and, together with isolation by distance, may lead to genetic isolation between populations and thus drive the evolution of lichens. 相似文献
13.
Coenogonium interplexum Nyl. is a green to yellow-orange filamentous lichen commonly found on tree bark, rocks, and soil. The mycobiont is the ascomycetous fungus Coenogonium. The ultrastructure of the lichenized phycobiont, Trentepohlia, closely resembles that of the non-lichenized form, a filamentous subaerial green alga. The mycobiont has a typical fungal ultrastructure, and the cell wall sometimes appears thinner at points of contact with the phycobiont wall. Several branched fungal hyphae are usually randomly arranged around a Trentepohlia filament, and may in some cases completely ensheath the alga. Although no haustoria were observed, this relationship may still be termed a lichen since there is some modification of the alga and the lichen is structurally distinct from the two symbionts. 相似文献
14.
15.
Sheeba S. Manoharan Vivian P. W. Miao Ólafur S. Andrésson 《Symbiosis (Philadelphia, Pa.)》2012,58(1-3):91-98
Lectins are a diverse group of carbohydrate binding proteins often involved in cellular interactions. A lectin gene, lec-2, was identified in the mycobiont of the lichen Peltigera membranacea. Sequencing of lec-2 open reading frames from 21 individual samples showed an unexpectedly high level of polymorphism in the deduced protein (LEC-2), which was sorted into nine haplotypes based on amino acid sequence. Calculations showed that the rates of nonsynonymous versus synonymous nucleotide substitutions deviated significantly from the null hypothesis of neutrality, indicating strong positive selection. Molecular modeling revealed that most amino acid replacements were around the putative carbohydrate-binding pocket, indicating changes in ligand binding. Lectins have been thought to be involved in the recognition of photobiont partners in lichen symbioses, and the hypothesis that positive selection of LEC-2 is driven by variation in the Nostoc photobiont partner was tested by comparing mycobiont LEC-2 haplotypes and photobiont genotypes, as represented by the rbcLX region. It was not possible to pair up the two types of marker sequences without conflicts, suggesting that positive selection of LEC-2 was not due to variation in photobiont partners. 相似文献
16.
Excessive nitrogen (N) deposition can impact lichen diversity in forest ecosystems, and this is a particular situation in China. Here, we examined the N uptake, assimilation, and the impact of excessive N deposition on the symbiotic balance of dominant epiphytic lichens in the subtropical forests in the Mts. Shennongjia of central China. The results show that lichen species took up, assimilated and utilized more ammonium than nitrate in a species‐specific way, following the increase of N availability. The photobiont of the lichens decreased with the increase of N concentration following an initial increase, while the mycobiont response to the N addition was not apparent. Considerable variation in response to excessive N deposition exists among the lichen species. Usnea longissima could regulate its N uptake, resulting in a stable photobiont‐mycobiont ratio among N treatments. In contrast, the photobiont‐mycobiont ratio of other four lichens increased initially but decreased when N concentration exceeded a certain level, and N stress may have broken the balance between photobiont and mycobiont of these lichens. Our results suggest that most epiphytic lichens in subtropical forest of central China could uptake and assimilate more ammonium than nitrate and that the balance between photobiont and mycobiont of many epiphytic lichens might change with the increasing N deposition load, which could impact the lichen diversity of this forest ecosystem. 相似文献
17.
Successful re-lichenization between the two bionts of the lichen symbiosis, the fungal mycobiont and its specific photobiont, is a process that is not well understood yet. To assess potential signalling between the two bionts during initial pre-contact, exudates of the Trebouxia photobionts of Fulgensia bracteata, Fulgensia fulgens, and Xanthoria elegans, of the Asterochloris photobiont of Lecidea lurida, and of the non-lichenizing green alga Myrmecia bisecta were investigated. The compounds identified in these exudates were tested with respect to their influence on germination and early development of the Fulgensia bracteata mycobiont. Additionally, carbohydrates (glucose, sucrose, ribitol) were tested to appraise their effect on the mycobiont growth patterns. Three hypotheses were confirmed: (i) photobionts exude various substances, (ii) the photobiont exudation pattern varies with the identity of the photobiont, and (iii) a pre-contact influence induces changes in the early development of the mycobiont of F. bracteata. This study gives comparative insight to exudates of lichen photobionts. In vitro photobionts differentially release compounds belonging to several substance classes which include indole-3-carbaldehyde, two cyclic dipeptides, and rhamnose. Two compounds had inhibitory effects on germination and germ-tube growth of the mycobiont and one other enhanced spore germination. Additionally, ribitol was found to elicit a strong effect on the mycobiont’s growth. In general, photobiont-exudation, its effect on the mycobiont, and the response to ribitol suggest that complex pre-contact signalling has a crucial role in lichen biont recognition. 相似文献
18.
This work deals with the survival analyses of the symbionts isolated from the lichen E. pusillum under desiccation and starvation stress. The mycobiont of the symbionts was under the desiccation in combination with starvation
stress, and under starvation stress alone as well. The phycobiont of the symbionts was under desiccation stress alone. The
experiments were detected by means of the biomass size, weight and cell density, deformity of the hyphae and cells, and metabolic
activity through SEM (scanning electron microscopy), TEM (transmission electron microscopy), FM (fluorescence microscopy),
spectrophotometry, and FCM (flow cytometry). The results show that the mycobiont can survive for seven months under desiccation
stress in combination with starvation stress, and for eight months under starvation stress alone. The phycobiont can survive
for two months under desiccation stress. It can provide a scientific basis for further research of the reproduction biology
of lichens and arid desert biocarpet engineering to fix sand and carbon. 相似文献
19.
Vicente Paulo da Costa Neto Janaina Barros Siqueira Mendes Ademir Sérgio Ferreira de Araújo Francisco de Alcântara Neto Aurenivia Bonifacio Artenisa Cerqueira Rodrigues 《Symbiosis (Philadelphia, Pa.)》2017,72(2):117-121
Nitrate uptake and nitrogen inclusion into amino acids were studied in the intact thallus and isolated bionts of the lichen Parmelia sulcata with the aid of mass spectroscopic tracing of heavy isotope 15N. The isolated photobiont, the green algae Trebouxia sp. did not take up nitrate, whereas the mycobiont and intact thalli were enriched in 15N when incubated with Na15NO3. Pulse feeding experiments with intact thalli followed by separation of photobiont showed that the labelled nitrate was originally assimilated by the mycobiont and only after that was detected in the photobiont. The isolated mycobiont after pulse labeling excreted labeled compounds into the incubation medium. Amino acids were detected in the exudate. The quantities of two amino acids considerably exceeded those of the others. One was identified as alanine, the other could not yet be identified with certainty. Both of these high-quantity compounds were also much more enriched in 15N than the others. These two compounds are proposed to be the transport forms of nitrogen within the Parmelia sulcata thallus. 相似文献
20.
Lichens are an association of a photoautotrophic alga/cyanobacteria (photobiont) and a heterotrophic fungus (mycobiont) constituting the lichen thallus as a complex phenotype. Many mycobionts reproduce sexually and the ascospores are dispersed without the photobiont. For successful re-lichenization the specific photobiont must be recognized, contacted, and incorporated by the mycobiont. A so-called pre-contact stage has been postulated as the initial step of a gradual recognition process. In the present study, the effect of the specific Trebouxia photobiont, an unspecific Asterochloris photobiont and the non-lichenizing green alga Myrmecia bisecta on the development of the mycobiont Fulgensia bracteata was assessed by pre-contact assays. Three hypotheses were confirmed: (i) the pre-contact stage exists, (ii) it is characterized by morphological reactions in the development of the mycobiont, and (iii) the reactions depend on the interacting alga. Control conditions revealed a mycelial growth arrest but this effect was not observed in the presence of any of the three algae. Different algae induce distinct growth patterns with respect to hyphal length, morphological characteristics, and formation of mucilage. The specific Trebouxia photobiont had a positive impact on hyphal growth, branching frequency, and mucilage formation. These effects were less explicit with the non-specific Asterochloris photobiont. Myrmecia bisecta induced uncharacteristic growth patterns with pronounced hyphal growth and high numbers of aerial hyphae but less formation of mucilage. These results indicate that symbiont recognition mechanisms are established before physical contact. Pre-contact reactions may be an evolutionary advantage that supports the persistence of the mycobiont on newly colonized sites and improves the probability of re-lichenization. 相似文献